前驱体溶液等离子喷涂参数对涂层形貌的影响及沉积行为机理研究

Influence of Solution Precursor Plasma Spraying Parameters on Coating Morphology and Mechanism of Coating Deposition Behavior

目的对不同喷涂工艺参数下涂层的相结构、显微形貌进行研究,确定优化的喷涂工艺参数,讨论分析涂层的沉积行为机理。方法采用前驱体溶液等离子喷涂(SPPS)的方法制备纳米Yb_2O_3稳定的ZrO_2(YbSZ)涂层。在传统等离子喷涂的基础上,增加液料雾化装置,雾化喷嘴将溶液雾化后直接注入到等离子弧中,通过控制喷涂距离及喷涂功率,研究了涂层相结构、结晶度、晶粒尺寸以及显微形貌的变化趋势,并且结合显微形貌讨论了沉积机理。结果涂层呈现团聚大颗粒、纳米级粒子、大小均匀的孔隙三种显微形貌,大颗粒之间呈堆积形态。当喷涂功率为30 kW时,涂层呈现m-ZrO_2,平均晶粒尺寸达669 nm。随着喷涂距离、喷涂功率的增加,样品中检测到单一的t-ZrO_2相,而且纳米尺寸颗粒的数量大大增加,孔径变小。随着喷涂距离由60 mm增加到100 mm,平均晶粒尺寸先由429 nm减小到177 nm,随后又增加到319 nm。结论喷涂参数影响晶粒的结晶度、晶粒尺寸以及涂层的显微形貌,低功率下得到的涂层存在糊状未结晶组织。增大喷涂功率,可以有效增大结晶度和晶粒尺寸;随着喷涂距离的增大,晶粒尺寸先减小后增大。雾化液滴在等离子火焰中一般要经历浓缩、饱和、固化、析晶形核长大、粒子重熔扁平化的历程,喷涂功率越高,经历温区越高,液滴演变就越充分,通过优化工艺参数可以得到不同结构性能的功能涂层。

The work aims to determine the optimal spraying process parameters and analyze the mechanism of coatings deposition behavior by studying phase structure and microstructure of the coatings with different spraying process parameters.Nano-Yb2O3 stabilized ZrO2(YbSZ) coating was prepared by solution precursor plasma spraying(SPPS). On the basis of traditional plasma spraying, liquid atomizing device was added. The atomizing nozzle injected solution into plasma flame. The coating phase structure, crystallinity, grain size and microstructure were studied by controlling the spraying distance and spraying power, and the deposition mechanism was discussed in combination with microscopic morphology. The coating exhibited three microscopic morphologies: agglomerated large particles, nano-sized particles and uniform pores, and the large particles were stacked. When the spray power was 30 kW, the coating exhibited m-ZrO2 and the average grain size reached 669 nm. As the spraying distance and the spraying power increased, a single t-ZrO2 phase was detected in the sample, and the number of nano-sized particles greatly increased, and the pore diameter became small. As the spray distance increased from 60 mm to 100 mm, the average grain size was first reduced from 429 nm to 177 nm and then increased to 319 nm. The spraying parameters affect the crystallinity, grain size, and microscopic morphology of the coatings, and the coatings obtained at low power has a paste-like uncrystallized structure. Increasing the spraying power can effectively increase the crystallinity and grain size. As the spraying distance increases, the grain size decreases first and then increases. The atomized droplets in plasma flame generally undergo the process of concentration, saturation, solidification, nucleation and growth, particle melting and flattening. The higher the spraying power and the temperature zone are, the more complete the droplet evolution is. By optimizing the process parameters, functional coatings with different structural properties can be obtained.